The aim of this study was designed to investigate the possible beneficial effects of the thymoquinone (TQ) in streptozotocine (STZ)-induced diabetes in rats. The rats were randomly allotted into one of three experimental groups: A (control), B (diabetic untreated), and C (diabetic treated with TQ); each group contain ten animals. B and C groups received STZ. Diabetes was induced in two groups by a single intra-peritoneal (i.p) injection of STZ (50 mg/kg, freshly dissolved in 5 mmol/l citrate buffer, pH 4.5). Two days after STZ treatment, development of diabetes in two experimental groups was confirmed by measuring blood glucose levels in a tail vein blood samples. Rats with blood glucose levels of 250 mg/dl or higher were considered to be diabetic. The rats in TQ treated groups were given TQ (50 mg/kg body weight) once a day orally by using intra gastric intubation for 12 weeks starting 2 days after STZ injection. Treatment of TQ reduced the glomerular size, thickening of capsular, glomerular and tubular basement membranes, increased amounts of mesangial matrix and tubular dilatation and renal function as compared with diabetics untreated. We conclude that TQ therapy causes renal morphologic and functional improvement after STZ-induced diabetes in rats. We believe that further preclinical research into the utility of TQ treatment may indicate its usefulness as a potential treatment in diabetic nephropathy.